1. Field of the Invention
The present invention pertains to a positive displacement reciprocating piston pump driven by hydraulic piston and cylinder type actuators which are interconnected by a control circuit for driving the respective pump pistons in timed relation to each other.
2. Background
In the art of positive displacement reciprocating piston pumps there has been a need for improved hydraulically actuated pumps of the type wherein the working fluid pistons are connected to hydraulic linear piston and cylinder type actuators for driving the working fluid pistons through their operating cycles in timed relation. Hydraulically actuated pumps are particularly advantageous considering the ever increasing demand for pumps requiring greater power input based on the need for higher flow rates and working pressures.
Some of the preferred applications for pumps of this type include the delivery of drilling mud in well drilling operations, the injection of various types of fluids in producing hydrocarbons from subterranean formations and in high pressure and high flow rate fluid transport applications such as slurry pipelines and the like. Hydraulically actuated pumps are generally more compact for a given power rating as compared with pumps which are direct driven mechanically by a conventional engine or electric motor and are therefore particularly advantageous for certain applications such as portable drilling rigs and the like.
However, some of the disadvantages of prior art hydraulically actuated pumps pertain to the lack of a reliable and efficient control circuit for transferring the power fluid to and from the power cylinders and the provision of controls which will suitably time the actuation of the power cylinder pistons in multicylinder pumps. There is, of course, an ever present need for improved arrangements of valving and overall configuration of the power cylinders with respect to the working fluid cylinders. The present invention is directed to several improvements in hydraulically actuated reciprocating piston pumps which will be described in further detail herein.